This invention is directed to a strap cutter for the cutting of straps between the discharge pipe string and the power cable to the submerged electric pump motor as the discharge pipe string is pulled. The method comprises the steps involved in this procedure.
Most subterranean oil must be pumped from the ground. A casing extends from the surface down into the oil pool, and is perforated in the oil-producing zone to permit the oil to flow into the casing. A common oil recovery pump structure, especially found in the older, shallower oil fields, is a surface pump jack which pulls a pump rod which extends to a pump cylinder in the oil adjacent the bottom of the casing. An advantage of this structure is the fact that the motive unit is on the surface, and is easily accessible for maintenance. A disadvantage is the length of the pump rod string, which becomes very long for greater well depths.
Submersible pumps are now widely used for the recovery of oil. They comprise an electric motor-pump combination which is positioned in the lower portion of the casing in the oil pool therein. The discharge pipe string is directly connected to the pump to receive the pumped oil, and the pipe string also serves as a mechanical support for the pump and its motor. Of course, electric power must be supplied to the pump, and this is accomplished by a suitably shielded electric power cable which also extends down the casing, on the outside of the pipe string. In order to support the power cable, it is strapped to the outside of the pipe string with steel band straps.
As the pump is raised for service, the straps are cut. In prior operations, the straps have been manually cut with the use of a hand-carried conventional wire cutter. As the pipe string is raised, sections are removed and set aside in a conventional manner, and the power cable is wound up on an adjacent spool.
The manual cutting of the strapping is dangerous and requires a very low pipe string raising speed. Furthermore, the direct manual operation is dangerous in this close proximity to the moving equipment. Thus, there is need for an improved, safer strap cutter and method.